1. Field of the Invention
The present invention relates to a compression ignition type internal combustion engine. In particular, the present invention relates to a compression ignition type internal combustion engine that switches between spark ignition combustion mode and compression ignition combustion mode.
2. Description of the Related Art
Existing compression ignition engines perform compression ignition combustion mode in a region of low load and intermediate load, and perform spark ignition combustion mode in a region of high load. Referring to FIG. 10, an intake valve opens at a timing, and by a lift amount, denoted by reference symbol A, and an exhaust valve opens at a timing, and by a lift amount, denoted by reference symbol B or C during an intake stroke with this type of engine. A high temperature exhaust gas that is exhausted from the exhaust valve to an exhaust passage during an exhaust stroke recirculates to a combustion chamber, performing internal exhaust gas recirculation (EGR). As a result, inner portions of the combustion chamber are heated and compression ignition occurs. Further, there is a danger that knocking will be promoted during spark ignition combustion mode if a high temperature exhaust gas is used. It is thus preferable to keep the exhaust valve closed during the intake stroke. In JP 2001-349219 A, for example, exhaust valve control corresponding to an intake stroke during compression ignition combustion mode and corresponding to an intake stroke during spark ignition combustion mode is performed by utilizing an electromagnetic valve driver apparatus.
However, the electromagnetic valve driver apparatus described above is extremely high cost. Accordingly, there is a problem in that the final cost of the overall engine also becomes expensive. Further, complex control is necessary in order to open and close the exhaust valve corresponding to both compression ignition combustion mode and spark ignition combustion mode by using the electromagnetic valve driver apparatus. In addition, many existing engines perform valve control by using a cam. It is thus preferable to use the existing cam structure engines, without reconstructing the existing engines to incorporate the electromagnetic valve driver apparatus.